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131.
In 3 experiments, the role of item strength in the retrieval-induced forgetting paradigm was tested. According to the inhibition theory of forgetting proposed by M. C. Anderson, R. A. Bjork, and E. L. Bjork (1994), retrieval-induced forgetting should be larger for items that are more strongly associated with the category cue. In the present experiments, the authors varied item strength on the study list by manipulating the position of an item within its category (Experiments 1 and 2) and by the number of presentations in the study phase (Experiment 3). Contrary to the predictions from inhibition theory, in all 3 experiments, stronger items did not show more retrieval-induced forgetting than weaker items. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
132.
Visualization of agreement and discussion processes during computer-supported collaborative learning
This study examined the effects of the shared space (SS) on students’ behaviors in a computer-supported collaborative learning (CSCL) environment. The SS visualizes discussion and agreement during online discussions. It was hypothesized the SS would increase the media richness of the CSCL-environment, would stimulate critical and exploratory group-norms, would lead to more positive perceptions of online collaboration, and would have an impact on students’ collaborative activities. In total, 59 students working in 20 groups had access to the SS visualization, while 58 students working in 20 groups did not. The results show that students with access to the SS visualization: (a) perceived higher media richness; (b) had a more exploratory group-norm perception; (b) perceived more positive group behavior; (c) perceived their group’s task strategies to be more effective; (d) engaged in different collaborative activities and (e) performed better on one part of the group task. These results demonstrate the potential benefits of visualizing agreement and discussion during CSCL. 相似文献
133.
Houchao Xu Prof. Dr. Jeroen S. Dickschat 《Chembiochem : a European journal of chemical biology》2021,22(5):850-854
The diterpene spiroviolene, its diterpene synthase from Streptomyces violens and the experimentally determined terpene cyclisation mechanism were reported in 2017. Recently, the structure of spiroviolene was revised based on a total synthesis, with consequences for the cyclisation mechanism. Herein, a reinvestigation of the terpene cyclisation to spiroviolene and the mass spectrometric fragmentation mechanism investigated by 13C-labelling experiments are presented. 相似文献
134.
This work explores the possibilities to blend block copolymers, i.e., Pebax MH 1657, with a variety of cheap poly(propylene oxide)‐rich molecules which could potentially play a double role in the resulting membranes as dispersing/stabilizing agents in multi‐component casting solutions and as a gas transport medium in the final membrane. These membranes were prepared by solution casting and were characterized by differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, X‐ray diffraction, density measurements, and Fourier transform infrared‐attenuated total reflection, while additive incorporation was also studied with theoretical calculations. Gas permeation measurements showed that this approach resulted in increased permeabilities at the expense of mixed‐gas selectivity. An interpretation of the blend structure was finally made using gas transport models. The compatibility of these additives with the synthesis of selective gas separation membranes may enable a potential double role in membrane synthesis, i.e., as stabilizing agents in membrane synthesis and as a gas transport medium in the final membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46433. 相似文献
135.
Hafnium silicate (HfSiO4; hafnon) is under consideration as an environmental barrier coating material for high-temperature applications. However, its rate of formation from mixtures of monoclinic HfO2 and crystalline (β-cristobalite) SiO2 powders is unknown. Here it has been synthesized and its formation rate measured during their solid-state reaction at temperatures from 1250°C to 1400°C. Rietveld refinement of X-ray diffraction patterns indicates that at 1250°C the hafnon phase fraction increases linearly with time, while at the highest reaction temperature, the hafnon phase fraction exhibited a parabolic dependence upon time. Between these two limiting temperatures, a region of linear behavior preceded a transition to parabolic kinetics, with the transition occurring at an earlier time as the reaction temperature increased. Arrhenius relations fitted the kinetics of hafnium silicate formation in both the linear and parabolic regimes. Scanning electron microscopy indicated that the reaction proceeded by diffusion of SiO2 into HfO2, similar to the mechanism by which zirconium silicate has been formed from vitreous SiO2 and tetragonal ZrO2. The initial linear rate of reaction is consistent with the growth of the contact area between the SiO2 and HfO2 particles combined with rapid permeation of the Si4+ and O2− through the initial, incompletely formed hafnon. After a thin hafnon layer had formed between the reactants, the rate of hafnium silicate growth slowed and further growth was governed by the rate of diffusion of Si4+ and O2− through the reaction product consistent with the observed parabolic dependence of the phase fraction upon time. 相似文献
136.
Arjan Berntsen Yvo Croonen Coen Liedenbaum Herman Schoo Robert-Jan Visser Jeroen Vleggaar Peter van de Weijer 《Optical Materials》1998,9(1-4):125-133
Polymer LEDs have a number of attractive properties that make them suitable for many applications. Operating at low voltage, bright large-area devices can be made by simple technology. One of the limitations that prohibited industrialization of polymer LEDs was their limited lifetime. An overview of the improvement of polymer LED performance at Philips is presented. The progress during the last year is reflected by lifetimes of many thousands of hours for 8 cm2 devices that operate at daylight visibility under ambient conditions. Diagnostic measurements have been performed on polymer LEDs before and after stress testing, and on the materials used in these devices. These measurements have contributed to the understanding of the nature of the degradation of polymer LEDs. 相似文献
137.
High Stiffness Cellulose Fibers from Low Molecular Weight Microcrystalline Cellulose Solutions Using DMSO as Co‐Solvent with Ionic Liquid 下载免费PDF全文
Chenchen Zhu Anastasia F. Koutsomitopoulou Stephen J. Eichhorn Jeroen S. van Duijneveldt Robert M. Richardson Rinat Nigmatullin Kevin D. Potter 《大分子材料与工程》2018,303(5)
There is a need to develop high‐performance cellulose fibers as sustainable replacements for glass fibers, and as alternative precursors for carbon filaments. Traditional fiber spinning uses toxic solvents, but in this study, by using dimethyl sulfoxide (DMSO) as a co‐solvent with an ionic liquid, a novel high‐performance fiber with exceptional mechanical properties is produced. This involves a one‐step dissolution, and cost‐effective route to convert high concentrations of low molecular weight microcrystalline cellulose into high stiffness cellulose fibers. As the cellulose concentration increases from 20.8 to 23.6 wt%, strong optically anisotropic patterns appear for cellulose solutions, and the clearing temperature (T c) increases from ≈100 °C to above 105 °C. Highly aligned, stiff cellulose fibers are dry‐jet wet spun from 20.8 and 23.6 wt% cellulose/1‐ethyl‐3‐methylimidazolium diethyl phosphate/DMSO solutions, with a Young's modulus of up to ≈41 GPa. The significant alignment of cellulose chains along the fiber axis is confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and powder X‐ray diffraction. This process presents a new route to convert high concentrations of low molecular weight cellulose into high stiffness fibers, while significantly reducing the processing time and cost. 相似文献
138.
Jan Rinkel Dr. Martin Litzenburger Prof. Dr. Rita Bernhardt Prof. Dr. Jeroen S. Dickschat 《Chembiochem : a European journal of chemical biology》2018,19(14):1498-1501
The cytochrome P450 monooxygenase CYP267B1 from Sorangium cellulosum was applied for the enzymatic oxidation of the sesquiterpene alcohols T‐muurolol and isodauc‐8‐en‐11‐ol. Various isotopically labelled geranyl and farnesyl diphosphates were used for product identification from micro‐scale reactions, for the determination of the absolute configurations of unknown compounds, to follow the stereochemical course of a cytochrome P450‐catalysed hydroxylation step, and to investigate kinetic isotope effects. Overall, this study demonstrates that isotopically labelled terpene precursors are highly useful to follow cytochrome P450 dependent oxidations of terpenes. 相似文献
139.
Jeroen van der Hooft Stefano Petrangeli Tim Wauters Rafael Huysegems Tom Bostoen Filip De Turck 《Journal of Network and Systems Management》2018,26(1):51-78
Over the last years, streaming of multimedia content has become more prominent than ever. To meet increasing user requirements, the concept of HTTP Adaptive Streaming (HAS) has recently been introduced. In HAS, video content is temporally divided into multiple segments, each encoded at several quality levels. A rate adaptation heuristic selects the quality level for every segment, allowing the client to take into account the observed available bandwidth and the buffer filling level when deciding the most appropriate quality level for every new video segment. Despite the ability of HAS to deal with changing network conditions, a low average quality and a large camera-to-display delay are often observed in live streaming scenarios. In the meantime, the HTTP/2 protocol was standardized in February 2015, providing new features which target a reduction of the page loading time in web browsing. In this paper, we propose a novel push-based approach for HAS, in which HTTP/2’s push feature is used to actively push segments from server to client. Using this approach with video segments with a sub-second duration, referred to as super-short segments, it is possible to reduce the startup time and end-to-end delay in HAS live streaming. Evaluation of the proposed approach, through emulation of a multi-client scenario with highly variable bandwidth and latency, shows that the startup time can be reduced with 31.2% compared to traditional solutions over HTTP/1.1 in mobile, high-latency networks. Furthermore, the end-to-end delay in live streaming scenarios can be reduced with 4 s, while providing the content at similar video quality. 相似文献
140.
Peng Dai Ji-sheng Zhang Jin-hai Zheng Kees Hulsbergen Gijs van Banning Jeroen Adema Zi-xuan Tang 《水科学与水工程》2018,11(3):220-228
Dynamic tidal power is a new way of capturing tidal energy by building a water head using a dike perpendicular to the coast. This study explored the hydrodynamic mechanism of the water head across an intended dynamic tidal power dike system using the Delft3D-FLOW software module. The propagating wave was simulated in a rectangular domain with a horizontal sea bottom at a 30-m depth. A significant water head was created across the dike by blocking the water. The water head increased with increasing dike length and increasing undisturbed tidal current acceleration. The maximum water head for the dike with a length of 50 km, located 900 km from the western boundary, was 2.15 m, which exceeded the undisturbed tidal range. The time series of the water head behaved in a manner identical to the undisturbed tidal current acceleration. The distribution of the water head over the dike assumed an elliptical shape. A parasitic wave was generated at the attachment and scattered outward. The phase lag across the dike did not behave as a linear function of the detour distance. 相似文献